Where does the pressure come from that creates the mechanical force to extend the speed brake?

The mechanical force to extend the speed brake in the T-6 aircraft comes from the primary hydraulic system. This system is responsible for powering various flight control surfaces and other essential functions, including the speed brake mechanism. The primary hydraulic system generates the necessary pressure through a hydraulic pump, which is driven by the engine. This pressure is then used to actuate the speed brake, providing the required force to extend and retract it as needed for controlling airspeed and descent rate during flight.

The other systems mentioned do not supply hydraulic pressure for the speed brake. The emergency hydraulic system is designed for backup operations in case of primary system failure, while the landing gear actuator and the nosewheel steering assembly primarily operate within their respective systems and do not contribute to the operation of the speed brake. Understanding the role of the primary hydraulic system is crucial for recognizing how various components of the T-6 operate together to ensure effective flight control.